She made her debut as a singer in 2005 with “Omna Magni”, produced by Yoko Kanno. It was used as the ending theme song for the anime Sousei no Aquarion. In the April of the same year, she also debuted as a voice actress, starring as heroine Sakura in Tsubasa Chronicle and recording several songs for its soundtrack. She released “Amrita”, the ending song for the Tsubasa Chronicle film, as well as “Undine”, the opening theme for the TV Tokyo anime Aria the Animation, coupled with its inserted song “Symphony”.[1][citation needed] It achieved #25 on the Oricon chart.

In 2006, Makino released two songs from another TV Tokyo anime, Aria the Natural, the theme song “Euphoria” and insert song “Amefuribana”. They were released on one product and achieved #18 on the Oricon chart. She released her debut album, Tenkyū no Ongaku on 6 December 2006.

On 23 January 2008, Makino released her seventh single, “Spirale” as the opening theme of Aria the Origination. Coupled with the anime’s insert song, “Yokogao”, the single reached #20 on the Oricon chart. She also performed her first solo concert at the Fuchuno Mori Geijutsu Gekijo Wien Hall in Tokyo, where she sang and played the piano accompaniment for each song. She released her eponymous second album, Makino Yui in March 2008. It reached #22 on the Oricon chart. She graduated from Tokyo College of Music as a piano major in the same month.

She held her Holography concert at SHIBUYA-AX in 2011.

In March 2013, Makino was hired to sing and be the voice of "Hungry Zombie Francesca" in a national campaign to promote the Hokkaido region throughout Japan.[2]